In order to gain a deeper understanding of locomotion and the most effective means of treating patients with locomotor disabilities, we propose in-depth quantitative studies of walking and mechanisms which contribute to abnormal walking performance such as muscle weakness, incoordination, spasticity, and the amount of external force required from canes and crutches. All of the measurements will be compared with standards of normal variability, most of which have been completed and some of which we propose to do in the future. We will use these quantitative measurements to compare treatment procedures directed at improving the functional performance of patients with selected neuromuscular and skeletal disorders.